Joel and Jeff from time to time reference the social research backing their design decisions for Stack Overflow. Specifically I remember in one of the podcasts where they mentioned that time and again, people design social communities and as it grows, they get excited when they noticed certain trends. Then somebody more experienced tells them it's all been done before and just wait till you see how it changes when it grows to the next stage.

It seems they take a lot of care to try to understand how online communities work and design the software and user experience around those principles, in order to drive behaviors towards the site's goals.

I'd like to compile a list of references to some of the research they've mentioned, and what design decisions that research led to.

is definitely worth a read when researching social behaviour on SO. It condenses a lot of patterns and behaviours common on SO - in an exaggerated and cartoonized form outlining the worst of the worst in a theatrical way, of course. Still, there's a lot of truth in it.

A true piece of collective art IMO. Must be read including all comments, but should under no circumstances be read if you're new to Stack Overflow. :)